10 hour road trip. Observations/torque-tire question

First I'll say I like my TRD OR. I'd like to love my TRD OR, but a couple of things keep me from it. I drove it from OKC to Springfield MO this weekend and it's very hilly. I had my TSD done a couple of weeks ago and it took care of my R-D hesitation. This is the first time I've had to check out cruise control to see how it works. I drove with cruise on the entire way there. While it did hold 6th a little better, it would down shift to 5th on relatively small hills. While that doesn't bother me, it puts me in that 2000-2300 rpm range where I get the high speed vibration in my steering wheel that feels like I'm holding an electric toothbrush. Then, on steeper hills, it still shifts into fourth. It sounds like you've floored it with the noise it makes. I got 20.2 mpg on the trip there.

On the trip home, I did not use CC at all. I would drive 80 down the hills, and try to hold 70 or a little under going up the next hill. I pretty much kept it from down shifting but I should be able to use CC without irritation I would think. I got 22.5 mpg NOT using cruise control.

In town I love my truck. On the highway, I like my truck. It needs more low end torque, and not to have a high speed vibration at certain rpms. I think I can live with these issues since nothing's perfect, and nothing else out there really catches my eye. But, I wish I didn't have to.

Now my question. After getting it stuck big time in some muddy muck, and having a 1970s Chevy 4x4 pickup pull me out (with great difficulty), I'm certainly going to ditch the Goodyear Kevlar tires. They filled up with mud and became slicks. No self cleaning no matter how much I spun them. I think I've narrowed it down to Duratracs or Cooper AT3s. But, I want to move up in size from 265/70/16 to 265/75/16. Since I cruise at about 1800 rpms at 70 mph staying below the 2000s where the vibration starts, will the one inch larger size tire help or hurt? It should drop the rpms at the same speed, but when I reach a hill, is it going to downshift earlier due to even less torque now?

 

https://www.tacomaworld.com/threads/buzzy-vibration-at-certain-rpms-read-before-buying.397620

Hey buddy, check the thread above. Its not tire related at all. Hope this helps to explain one of your issues. Please post your observations in that thread

 

I think he was only talking about tires in how alarger tire would change his cruising RPMs for a given speed. Trying to avoid the vibrating RPMs.

I don't know exactly what your new RPM would be but there are guys running that sized tire maybe they will chime it.

 

Hmm, the Duratracks look better and both can be had in a 6-ply as well. The Coopers in a P and lighter.
The Coopers have a pretty good reputation too. They just won't look at good as the Duratracks IMHO.

I can't comment on the gearing vs tire diameter question but I would say so. Thing is you would need a lift to go any taller than the 265 I think. The 265/75s do look better on the stock wheels though.

 

Yep, fully aware that the vibration has nothing to do with tires. The tire swap has to do with getting stuck and needing more aggressive tread than the OEM tires. I'd like to move up a size but I wonder what it will do relative to shift points and rpms

Basically, will it hurt or help my cruise control issues....

 

Agreed. The practical side of me says buy the Coopers. For a tire that will see more pavement than mud, it's the logical choice. But dang it, I like the looks of the Duratracs. And I bet they are a little better off road. I'd probably buy a KO2 but can't get a C instead of E in the size I need.

A lift will be coming, I'm just waiting to get most of my truck problems worked out before doing so.

 

I keep hoping and hoping BF Goodrich will make a 265/75/R16 KO2 in a 6-ply!

 

I've got AT3's on my work truck (2500 Duramax) and Duratracs on my Taco. The AT3's are a great all-round pavement / gravel road / field-pasture tire but I really like the Duratracs for anything more off road. The on-road manners of the Duratrac are actually quite good.

 

You need to get the RPM's up to get power/torque. The tranny is programmed for best mpg's, so it's going to feel underpowed unless you use the sport shift or ect button to keep the rpms up. You were basically hyper-miling to some extent on the way home, so that got you some additional mpgs. My accord is rated at 26 combined and I average 34-35 mpgs consistently on my 30 mile commute. That's a 5spd manual though. If mud is a concern I'd go with the Duratrac's over the AT3's, but a larger, heavier, aggressive tire isn't going to improve the power feel or the vibes..

 

Oh I forgot to add,

Do yourself a great favor and go ahead and use a reputable wheel/tire facility to have your tires mounted and balanced, what I mean is I've got five brand new Hankooks sitting in my storage shed that are going on my 4 cylinder Tacoma on Wednesday. I was going to have the dealership do it because it would save me about 40 bucks but I went ahead and made the appointment with Discount Tire as they charge the same whether I bought them from them or on their eBay store and they have a guarantee for the balancing and the rotate and balance for the life that I have them, as well as replacing the O-rings and rebuilding my factory TPMS valve stems.

Yes I'm spending just a little bit more, but the peace of mind is far worth more than what I'm spending in the difference.

 

Both 6th and 5th are overdrive ratios, so it can be normal to drop to 4th (which is 1:1) if you want to maintain 80 mph uphill.

I run Duratracs in 265/75-16 load range C in the winter and Hankook ATm in P-metric in the other 3 seasons. The Duratracs are noticeably harsher over potholes. There's also a drone on the highway similar to big rig tires, but it's still a lot more tolerable than the Firestone Winterforce snow tires I had before. Keep this in mind if you do a lot of highway cruising.

 

I had smaller Duratracs on my 1999 Taco, and they were very noisy after I got about 5-10k miles on them. If you just want them for mud, they will be great. But if you are already unhappy with the buzzing, you will hate how noisy the Duratracs get after a while when you are cruising on the highway.

 

Regarding your question about changing shift points, you are looking about a 3% (~2mph) difference between the 2 tires according to the Discount Tire calculator. You should run at slightly lower RPMs to achieve the same speed, so yes, theoretically if you are worried about downshifting for torque on hills, it will do that more often. But I actually doubt the difference based on tire size alone will be all that noticeable. However, the more aggressive tread is also going to result in slightly higher rolling resistance, which will add to the problem. How much it will add is anybody's guess, and might actually start to make enough of a difference that it would bug you if you already don't like the downshifting.

 

Yeah, that was my guess as well. I may just stay with stock size for now and hope Toyota comes up with a fix for the high speed vibration. If so, I'll look at better suspension as well as tires again.

 

Don't know if it helps but when I went from the stock Dunlops to 265/75R16 Cooper ST load range E I dropped about1-1.5 MPG still consistently getting 20.5-21.5. When these are replaced I'm going to Cooper AT3 235/85's.

 

This.. I'm guessing you're vibe is due to a tire being out of balance. It would be a good place to start at least.

 

Nope, nothing to do with tires. There's a thread here on TW about the vibration that's over 100 pages. One guy said he drove 4 new trucks at the dealership and they all had the vibration. It's typically around 2000 to 2500 rpm. Mines 2000 to 2300 rpm. On a poll on TW about 40 percent who responded had the vibration. My question is will a larger tires help or hurt my shifting times base on rpms.

 

It will shift down from (6th to 5th to 4th. etc..) quicker to find more power with larger tires. So if your going up a slight incline with 265's and it normally shifts from 6th to 5th to traverse the hill, then with 285's it might shift to 4th to take the same incline. This will decrease your mpg's slightly and feel like you lost a little power. It won't help the issue you described in the first post. It would go to 4th gear more often, not less.

Smaller tires and/or less aggressive tread would have less rolling resistance and allow the truck to keep momentum better, but I don't think you're looking to go that route.

Other than that you're at the mercy of the transmission programming. It sounds normal to me. That's why I always buy a stick shift. Then I'm always in the right gear. I hate auto tranny's post 2010..

 

Building on what I said here..

You can look at improving aerodynamics as well as dropping any unneeded weight. buying a tonneau cover and the front air damn would decrease drag. Smaller and less aggressive tires/wheels weigh less and have a multiplier effect. If you cut 10lbs from each wheel/tire that would be 40lbs of saved weight. But it's a 10:1 ratio of rotational mass to dead weight, so it's really like removing 400lbs of dead weight from your truck bed.

Beyond lighter wheels and tires and better aero, you're looking at extreme weight saving measures. Remove any unneeded gear, lose the spare wheel/tire/jack and carry fix a flat kit, go on a diet...

Good luck.

 

I ran duratracs on my tundra, E load range and they were quite and smooth, I had gotten 55k on them ( highway driver ) 265/70/16 and they where just getting to the wear bars and still had grip, smoothness and about 1/2 inch of lugs on the tire.